MULTIPLE-SCATTERING X-RAY-ABSORPTION ANALYSIS OF SIMPLE BROMINATED HYDROCARBON MOLECULES

A multiple-scattering analysis of Br K-edge extended X-ray absorption spectra of some brominated hydrocarbon molecules is presented. A new method for calculating multiple-scattering contributions and to perform data analysis has been used. The brominated hydrocarbons solubilized in different molecular assemblies and macromolecular systems may be used as probe molecules. An accurate analysis of the intramolecular contribution to the absorption spectra allows the possibility of identifying the intermolecular contacts related to the systems in which these moleculesare solubilized to beevaluated. We present a very accurate X-ray absorption spectroscopy investigation of several brominated hydrocarbons (bromoethane, 2-bromopropane, 2-bromo-2-methylpropane, and bromobenzene), taking into account the three-body multiple-scattering contributions which are found to give a detectable signal to the X-ray absorption cross-section. The presence of double-electron excitation edges is reported. The inclusion of these additional edges allowed us to obtain a very good agreement between the calculated and the experimental spectra and reliable values of interatomic distances. Moreover, mean values and standard deviations of the bond-angle distributions have been determined. The results indicate that the molecular geometry of the brominated aromatic hydrocarbons gives rise to a strong multiple-scattering signal which could compromise the determination of the intermolecular contacts. The aliphatic brominated hydrocarbons seem to be more suitable to be used as probe molecules